In the market for green energy

Fruit and vegetables from a London market that can't be sold are being treated through anaerobic digestion and converted into electricity, as Stuart Spear reports

Hackney Market in full flow

In recent months fruit and vegetable traders in Ridley Road market, north London, have been bagging up their green waste to be converted into electricity. It is, says Larry Julian, chair of the Ridley Road Market Traders Association, the ultimate form of green energy as vegetable waste that in the past went to landfill is transported to Bedfordshire for anaerobic digestion.

Julian and his brother are fourth generation fruit and vegetable traders in one of the capital's largest markets. They agreed last November, along with the market's other 35 fruit and vegetable traders, to be part of a trial between the AD specialist BiogenGreenfinch and Hackney London Borough Council which is about to be rolled out across more of the council's markets.

"This is the 21st century and just throwing your fruit and veg on the floor at the end of the day is just no longer the answer," says Julian. "We are very much in favour of this as anything that is good for the environment has to be carried through."

AD's environmental credentials are impressive. Each year we throw out between 12 and 20M tonnes of food waste, 8.3M tonnes of which is collected by local authorities.

According to Defra, every tonne of food waste digested rather than sent to landfill cuts our emissions by between 0.5 and 1 tonne of CO2 equivalent. The main culprit is the methane emitted when food waste is landfilled, which is 20 times more potent a greenhouse gas than carbon dioxide.

Then there is the biofertiliser by-product that can be used on crops and the energy produced by converting methane into electricity. Government figures show that 5.5M tonnes of food waste is enough to meet the power needs of 340,000 households.

AD is not limited to food. When you throw agricultural waste and sewage sludge into the mix, the government estimates that it could account for up to 7.5% of the renewable energy we will have to produce by 2020 to meet our obligations under the Renewable Energy Directive.

For BiogenGreenfinch this means having to keep up with a very fast expanding market. Already processing thousands of tonnes of waste food collected from local authorities, supermarkets and manufacturers, along with slurry from its own farms, the company plans to build another 10 plants over the next five years throughout the UK. It currently has three plants - Biocycle in Shropshire, Twinwoods in Bedfordshire and Westwood in Northamptonshire.

Where the Bedfordshire-based company believes it has the edge on competitors is that it has developed the technology to exclusively process food waste.

Plants that only process food waste produce more methane that agri-AD plants. This methane can then be used to generate electricity. At Twinwoods in Bedfordshire, the plant produces 1.85 megawatts of electricity, which is fed into the national grid.

According to Simon Musther, head of commercial operations for BiogenGreenfinch, it only takes nine months to get a plant built and running. "At the moment demand is outstripping supply. We have people calling us up from quite far distances saying they want to send their waste to us," says Musther.

"We plan to build our sites so they accept 45,000 tonnes of waste a year, which is based on our assessment of the amount of waste generated in a 30-mile radius of each plant."

One obstacle to AD meeting its full energy potential is the number of local authorities stripping food out of their waste streams. According to WRAP, 94 UK authorities separate food waste, although it expects numbers to rise as the cost of landfilling biodegradable municipal waste increases.

BiogenGreenfinch's customers include Surrey County Council, Ealing LBC, Hounslow LBC, Richmond LBC, Central Bedfordshire, Luton and Flintshire in Wales. Until more plants come on-stream and more local authorities segregate food the challenge will be to source waste in enough volume and close enough to existing plants to make collections economically viable.

That is why this latest project with Hackney LBC to process food waste from Ridley Road market may prove to be a win-win for local authorities wanting to cut landfill costs and companies keen to convert food waste to energy. Since November Ridley Road market has produced 10-tonnes every three weeks for conversion into energy.

Rather than collecting from the markets, BiogenGreenfinch provides specially-designed food skips at the Hackney transfer station that it picks up when full. The cost to local taxpayers of sending market food waste for AD is almost half that of sending the equivalent waste to landfill.

"Now we understand volumes and benefits we are starting to knock on the doors of other authorities," says Musther.

Back at Ridley Road market, Julian has a note of caution for councils interested in turning market waste to energy. For the scheme to reach its full potential he believes that councils must remember to spend time re-educating stall holders about the importance of collecting their green waste.

"I'd like to see the council making more effort to keep talking to the traders to get them to change their ways," he says. "For the old traders it takes time to change habits and the new traders will look at what they do and follow suit. A bit more hand holding would make all the difference."